Flexibility and adaptability in a space environment is needed to further exploration into space. In addition, the ability to protect seals when not in use is needed for dust environments, debris containing environments, mining applications, petroleum exploration, petroleum refining, petroleum handling, chemical exploration, chemical refining, chemical handling, superconductor manufacturing environments, semiconductor manufacturing environments, combat environments, medical environments, including medical usages within a human body, and underwater environments.
A mechanism being developed to join space vehicles and structures, called the Low Impact Docking System (LIDS) is designed to be the interface between pressurized manned and autonomous modules. The LIDS is designed to overcome the limitations of mechanisms currently in use for the human exploration of space. The systems currently in use, including the Common Berthing Mechanism (CBM) used on the International Space Station, can function either as a docking or berthing mechanism, but not both. (Docking refers to the mating between two free-flying structures or vehicles which are generally crewed. Berthing refers to the joining of two structures typically by using a robotic arm and are generally unmanned autonomous modules.) These current systems are composed of two non-identical halves (a male and a female), limiting their functionality to mating with structures having the opposite gender interface.
A current system used in space development is known as the LIDS system and is designed as an androgynous system, such that each system half is an identical replicate of any other. Any two vehicles or modules each having an LIDS incorporated can mate with the other without regard for gender. During mating, one LIDS system is selected as the active side and the other is selected as the passive side, effectively designating a male and a female in situ. This feature of the LIDS provides an additional layer of fault tolerance, since either half can be designed the active half. The androgynous nature of the LIDS, however, creates challenges for the sealing interface between the two pressurized modules. Since each system half is an exact replicate of its mating counterpart, the gas seals must interact with a replicate (in a seal-on-seal configuration) instead of a more conventional flat surface.
The LIDS can be designed to accommodate NASA's future space exploration missions, such that it must operate in low-Earth-orbit (LEO), in high-Earth orbit, on the lunar surface, and in deep space locations. Therefore, the seal's ability to resist the detrimental effects of space environments is required. Each of these environments offers unique exposures to temperature, solar radiation, reactive elements, debris and mission duration.
Degradation of polymers can occur due to exposure to solar ultraviolet radiation (UV). In the environment of space, the UV is energetic enough to break polymer bonds. Degradation, in the form of scissioning and crosslinking, can modify the material's surface characteristics and cause seal material mass loss. In Earth orbit, the (UV) dissociates oxygen molecules creating monatomic oxygen (AO). Monatomic oxygen is very reactive and aggressively erodes most organic compounds.
Micrometeriods and man-made debris threaten the integrity of all Earth-orbiting and transitory spacecraft The relative speeds at which particles impact the spacecraft (>20,000 miles/hour) can easily damage a sealing surface that needs to achieve a near-hermetic seal.
The Martian surface, as recorded during the Mars Pathfinder mission is also a harsh environment. The atmospheric pressure was below 1% that of the earth (<1 kPa) while the temperature fluctuated 60° C. daily, but never reached above 0° C. The Martian weather included dust-devils and dust settling from the atmosphere. The dust particles contain peroxides that may react with seal materials.
The operating environments of interplanetary missions are non-specific and are assumed to be similar to those of lunar missions. However, the dormancy time (the time during which the seal is exposed on the exterior of the space module, but not mated to another module) would be far longer. Since the travel time to the moon is on the order of days or weeks, the dormancy period would be at most years. Since the travel time to other planets would be years, the expected dormancy period may be decades.
Throughout the dormancy period, the sealing surface must be protected from exposures to temperature, solar radiation, reactive elements, and debris, so that a near-hermetic seal can be formed when the seal is mated with its replicate.
Chemical and petroleum handling, refining and exploration present similar challenges regarding contamination and destruction of sealing surfaces as exposure to air and chemicals used in the process degrade current sealing surfaces. The mining industry presents similar challenges regarding dust contamination. Protection in these environments being key to prevent seal contamination.
Underwater exploration presents challenges similar to the space environment as seal exposure to environmental factors must be minimized in order to preserve the seal integrity prior to its engagement. When coupled with usages such as mining, petroleum exploration and handling and energy exploration and handling, underwater environments present a need in the art for a protection of the sealing surfaces utilized.